Landing gear



Sept. 4, 1945. w. c. TRAUTMAN' LANDING GEAR Filed Sept. 26, 1941 FIG.

WALTER C. TRAUTMAN FIC-3.2.-

ATTORNEY airplane Patented Sept. 4, 1945.

UNITED STATES PATENT ori-ICE LANDING GEAR Walter C. Trautman, Burbank, Calif., assignor,

by menne assignments, to Bendix Aviation Corporation, South Bend, Ind., a corporation of Delaware Application September 26, 1941, Serial No. 412,469

2 Claims.

This invention' relates to a landing gear for airplanes, and more particularly to a retractable wheel strut.

Itisfan object of the invention to provide a retractable wheel strut having an automatically operable locking member to hold itin an operative position.

It is another object to provide a retractable strut having a retracting motor, the initial motion of which unlatches the locking member.

A further object is to provide a strut having a pivot'about which the strut is rotated to effect retraction of the strut, and having a, pivotally mounted retracting and extending motor connected thereto whereby the motor rotates as the strut rotatesI on is retracting motion.

Still another object is t'o provide a strut having a retracting motor rotatable on a' pivot shaft wherein power is supplied to the motor through its Pivot shaft.

Another object is to provide a strut having a moveable retracting motor which is supplied with power through non-flexible conduits.

Still another object is to provide a retractable wheel strut of novel and simplified construction.

In the drawing:

Figure l is a view in elevation of part of an in vertical section in which is mounted a wheel strut made in accordance with the presentI invention. The operative position of the strut is shown in full lines and retracted position of the' strut is shown in broken lines;

Figure 2 is an elevation view partlyin section of the strut of Pig. 1, together with its retracting motor;

Figure 3 is a sectional view along the lines l-l of Fig. 2 showing the construction of the retracting and extending motor; and

Figure 4 is a sectional view along the line 4 4 of Fig. 3 showing the details of the iluid paths vat the pivot of the motor.

Referring to Fig. 1, an airplane I having an opening I2 on the undersurface thereof, has a step or recess I4 seen in the open part of Fig. 1. 'Ihe part of the airplane shown is a tail section and the invention is illustrated as a. tail wheel. although it could also be shown as a main wheel or nose wheel. Mounted in airplane I0 vis a transverse pivotl shaft Ii, on whichV is pivotally mounted a collar I 'I rigidly secured'to an outer cylinder Il of an airplane shock strut.

At the lower end of cylinder Il and telescoping therein is a cylinder 2l. Mounted on the lower end of cylinder 2l is a wheel fork 2l to which 26 and cylinder I 8 are kept from relative rotation by torque arms 22 and 24 fastened to cylinder I8 and to fork 26 respectively.

, The cylinder I8 is held in an upright position by a lock pin 20 in the upper end of cylinder I8 fitting into step I4 of the airplane III. The strut as a whole is rotated in retraction or extension by a piston-cylinder motor 24 having 4a piston rod 32 connected to cylinder I8 and lock pin 30I Piston cylinder motor 34 is pivotally mounted on a transverse pivotI shaft 38 secured to the airplane III. A cable 38 which is actuated by the pilot of the airplane, passes around a pulley A mounted on pivot shaft I8. and is secured to a centering latch pin on the shock strut, the construction of which will be later explained. A

Referring to Figure 2, the parts already ,described are readilyidentiiled'.4 The collari l1 pivots about shaft I6, and is rigidly fastened to` centers the upper end of cylinder 2l in cylinder III lthough torque -arm 24 is securely`r'fastened to fork 28,11; will be noted that the torque arm 22 is fastened to a collar 48 rotatably mounted on cylinder I8. Collar 46 may be kept from rotation, however, by a centering latch pin 48 held in an ear 5I) welded to the outer side of cylinder I8. A spring 52 normally urges the centering latch pin 48 into engagement with the rotatable ring 48 to prevent relative rotation of thering 46 to the cylinder I8. When in this position, the fork 26 'is held from relative rotation to the cylinder I8. If, however, the pilot should pull on'w'lre-38 and withdraw pin 4l against the compression of spring 52, the wheel 2l would then have arfree castoring action such as is desirable il secured an airplane landing 'wheel 2l. Fork u in maneuvering an airplane in a hangar.

The details of construction of the lock pin 30- are also'shown'in Fig. 2. The pin 30 is longitudinally moveable in a housing I4 secured to the upper end of cylinder Il, and the pin` 20 is urged upwardly by a.- compression spring It retained in housing I4. TheA pin '2l hasaxial 2 e y slot 88 through which passes a pin"88, secured to a forked member 82 on the upper end of piston rod 82.- Pin 88 passes through ythe head 84 also, through a slot 84 in the housing 84, which slot is shown in dotted outline VIustbelow the bottom end of lock pin 88. This construction allows the initial rotation off-the reti-acting motor u to pun the pinf88 dowm'ivardly todisengage it from step leading therefrom and communicating with the I bottom end of cylinder 84 through a passage 14. A hydraulic conduit 18 is connected to the outer end of passage 18. Suitable .packing surrounds pivot shaft 88 near the radial bores 18 and may be Aof the Chevron type 1I held by a compression spring 13. Also shown in Fig. 3 is the piston rod 32 having secured to the lower end, a piston 83. Fluid passes to the upper side of piston 88 through a conduit 85 fastened to the cylinder 84. The. details of construction of the hydraulic fluid path to conduit 88 are shown in Fig. 4. An 'axial passage 18 in the right end of-pivot shaft I8, communicates with radial bores 88 thereinv which in turn communicate with a passage 82 drilled in a 'projection 84 of the cylinder 84. .Chevron packing 1I spread by compression spring.13 also seals the pivot Ajoint near radial bores 88. Conduit 88 in turn yis secured to projection 84,. and passes upwardly to the upper end of cylinder 84 Aas shown in Fig. 2. A hyq draulicconduit 88 passes fluid to the outer end of axial passage 18. l

From the foregoing? description it will be apparent that there areno flexible conduits lneces-` sary for the motor 84 to accommodate its rot'ation as it retracts or extends fthe strut. This feature is importantin eliminating a source of wear and therefore future trouble in the retracting motor. e

The construction of the locking pin 88 with relation to theretracting motor 84 and its pivot rod 82 allows the locking pin 88 to move freely into step I4 as the strut is extended. This .con- I struction also allows the reti-acting motor to unlock the strut with its initial motion, rather than having a separate unlocking device.

In operation, the strut is extended as shown in'full lines in Fig. 1, the lock pin 88 fitting in the step I4 to hold the strut in an upright position. Upon landing the pilot will usually desire a non-castoring action from` the wheel shown, which 'is a tailwheel, Yalthough it could be a main wheel of an airplane as far as this invention is concerned.' After the airplane is landed, and the pilot desires to maneuver the airplane to enter a hangar or' to get oif of a runway he will pull upon wire 88 which will withdraw centering latch pin` 48, allowing the ring 48 to rotate freely on outer cylinder I8. The

torque arms 22 and 24 will not then prevent relative rotation of the wheel with relation to the strut I8. Upon take-oil' thepilot will prob-v ably not desire'a swivel action, and will allow tige pin 48 tc connect the ring 48 to the cylinder When the airplane has left the groundY upon the lock step.

wheel to reducethe aerodynamic friction of the airplane. By manual operation of a hydraulic valve (not shown) he will cause fluid to iiow into conduit 88 which passes fluid into passage 18, with axial bores 88 into passage 82 (Fig. v4) and into conduit 88 .which leadsto the upper part 'of the cylinderl 84 as shown in Fig. 3. At the same time conduit 18 is opened to exhaust. Fluid then acts upon the upper surface of piston 88 forcing it downwardly, displacing uid out through conduit 18, and causing piston rod 82 and fork 82 secured thereto to. pull pin 88 (Fig. 2)Y downwardly. VPin 88 will then slide freely in slot 84 pulling pin 88 downwardly until it 'is removed from the step -I4 (Fig. 1). When the pin 88 reaches the bottom end'of `slot 84 it will then pull against the cylinder I8 causing it to rotate about its pivot shaft I8 to the position shown in dotted outline in Figure 1. In this position the strut is now completely retracted, offering no resist.-

ance.

Upon landing the pilot will desire to extend the strut, and for this purpose vwill operate a manual valve (notl shown) to pass fluid to conduit 18, and to exhaust conduit 88. Fluid will then press against the upper end of slot 84 in head 54, rotating the strut as a whole to 'the upright position shown inV full lines in Fig.' 1. When the strut near its uprightl position, the pin '88 will strike part of the airship in which is formed step I4, and will be forced downwardly 1. In an airplane, a wheel strut installation` comprising, a shaft, a.V wheel strut pivotally mounted thereon, a pin mounted on the upper end of said wheel strut and having an elongated slot therein, the lstrut being recessed to receive the pin and being slotted in a like direction with the pin, resilient means urging said pin outwardly from said strut, a `lock step in said airplane envgageable by the pin to lock the strut in an operating lpomtion, an actuating cylinder separate from said strut and pivotally mounted in said airplane, and a pin passing through said strut and pin slots to form a lost motion connection between them and the actuating cylinder, so that the pin is withdrawn upon the initial movementof the actuating cylinder in retraction and thev pin may be depressed upon extension to engage 2. An airplane wheel strut assembly comprising. a wheel strut adapted to be pivotally mounted, 'a slidable lock pin on the upper endthereof, the movement of which is: limited by stops, resilient means urging said pin outwardly from said strut, and a separate actuating cylinder connected directly to saidpin to retract and extend said strut. Said. connection vbeing a lostmotion connection to allow theV pin limited depressing action upon extension, and to permit unlocking the pin upon retraction. v

' WALTER c. 

